// Copyright (c) 2009 libmv authors.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.

#ifndef LIBMV_IMAGE_IMAGE_CONVERTER_H
#define LIBMV_IMAGE_IMAGE_CONVERTER_H

#include "libmv/image/array_nd.h"

namespace libmv{

template<typename T>
// The factor comes from http://www.easyrgb.com/
// RGB to XYZ : Y is the luminance channel
// var_R * 0.2126 + var_G * 0.7152 + var_B * 0.0722
inline T RGB2GRAY(const T r,const T g, const T b)
{
  return static_cast<T>(r * 0.2126 + g * 0.7152 + b * 0.0722);
}
/*
// Specialization for the uchar type. (that do not want to work...)
template<>
inline unsigned char RGB2GRAY<unsigned char>(const unsigned char r,const unsigned char g, const unsigned char b)
{
  return (unsigned char)(r * 0.2126 + g * 0.7152 + b * 0.0722 +0.5);
}*/

template<class ImageIn, class ImageOut>
void Rgb2Gray(const ImageIn & imaIn, ImageOut * imaOut) {

  assert( imaIn.Depth() == 3 );

  imaOut->Resize(imaIn.Height(), imaIn.Width(), 1);
  // Convert each RGB pixel into Gray value (luminance)

  for(int j = 0; j < imaIn.Height(); ++j)
  for(int i = 0; i < imaIn.Width(); ++i)  {
    (*imaOut)(j,i) = RGB2GRAY(imaIn(j,i,0) , imaIn(j,i,1), imaIn(j,i,2));
  }
}

} // namespace libmv

#endif  // LIBMV_IMAGE_IMAGE_CONVERTER_H
